Soil quality index (SQI) as influenced by rubber land use among different districts of hilly zone of Karnataka
Author(s):
Niranjana KS, Yogendra K, Mahadevan KM and Ashok LB
Abstract:
The hilly zone of Karnataka is characterized by heavy rainfall, loss of nutrients through leaching, top soil erosion, high soil acidity etc. which leads to acute soil degradation. With the intensification of agricultural practices to get enhanced returns, there is a new emphasis on using the concept of soil quality. Quantitative assessment of soil quality is done to determine the sustainability of land uses in terms of environmental quality and plant productivity. Thus, a study was conducted to address the selection of most appropriate soil quality indicators and to quantify the soil quality index (SQI) under rubber land use system among Shivamogga, Chikkamagaluru and Kodagu districts which majorly represents the hilly zone of Karnataka. About 160 surface samples at 0-15 cm depth were collected from different locations among three districts and analysed for 24 physical, chemical and biological soil attributes. Principal component analysis (PCA) approach was employed to get the minimum data set on the measured attributes. The data obtained which was subjected to PCA provided 8 principal components (PC) with eigen values >1 and explaining at least 5 per cent of variance in the data set. The 8 PCs together explained 84.36 per cent of total variance. Based on the rotated factor loadings of soil attributes, the selected minimum data set were sand from PC-1, exchangeable Mg (Mg) from PC-2, soil organic carbon (SOC) from PC-3, available nitrogen (N) from PC-4, clay from PC-5, zinc (Zn) from PC-6, earthworm population density (EWPD) from PC-7 and boron (B) from PC-8. Indicators were transformed into scores (linear scoring method) to calculate the SQI. It ranged from the least of 0.39 in Shivamogga, 0.40 in Chikkamagaluru and the highest of 0.47 in Kodagu districts within rubber land use system of hilly zone of Karnataka. The overall contribution (in per cent) in the determination of SQI was in the order of sand (41.22), Mg (15.62), SOC (13.31), N (7.33), clay (7.09), zinc (6.16), EWPD (5.43) and B (3.82).
